Comparison
215/55 R17 vs 275/40 R18
Going from 215/55 R17 to 275/40 R18 steps up to a 18-inch rim while trimming sidewall to stay near OEM rolling diameter. This sizing approach keeps overall diameter very close to stock. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement.
The speedometer offset is mild and well inside what most cars can tolerate without recalibration. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 275/40 R18 is 8.9 mm taller than 215/55 R17, shifting the speedometer by +1.33%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+8.9 mm
1.33%
Speedometer at 100
101.3 km/h
+1.33% error
Ground clearance
+4.5 mm
ride height delta
Sidewall change
-8.3 mm
revs/km: 470.0
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/compare/215-55-r17-vs-275-40-r18Detailed comparison
| Metric | 215/55 R17 | 275/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 668.3 mm | 677.2 mm | +8.9 mm (+1.33%) |
| Sidewall height | 118.3 mm | 110.0 mm | -8.3 mm |
| Circumference | 2.100 m | 2.127 m | +28.0 mm |
| Revs / km | 476.3 | 470.0 | -6.3 |
| Ground clearance | reference | +4.5 mm | +4.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.3 km/h | +1.33 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Speedometer impact
At a true 100 km/h, your dashboard will read 101.3 km/h after switching to 275/40 R18 — a +1.33% offset. Use the speedometer error calculator to recheck for other indicated speeds, and the speedometer error guide for the full background.
Ground clearance change
The new tire's half-diameter changes ride height by +4.5 mm. Small differences are absorbed by suspension travel, but anything beyond ±10 mm can affect headlight aim, fender clearance and bump-stop margin. See the plus-sizing guide before committing.
Back to
215/55 R17
Back to
275/40 R18
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